In the heart of China, researchers at the Key Laboratory of Biology and Sustainable Management of Plant Diseases and Pests of Anhui Higher Education Institutes, led by Bo Su, have made a significant breakthrough in understanding maize’s defense mechanisms. Their work, published in the journal ‘Plants’ (which translates to ‘Plants’ in English), focuses on a protein called ZmCpn60-3, opening new avenues for enhancing disease resistance in crops.
Chaperonin 60 proteins are known to play crucial roles in plant growth, development, and stress responses. However, their specific functions in maize have remained largely unexplored until now. Su and his team cloned the ZmCpn60-3 gene from the maize inbred line B73, revealing a protein composed of 605 amino acids. Through phylogenetic analysis, they discovered that ZmCpn60-3 is highly similar to OsCPN60-1, a protein belonging to the β subunits of the chloroplast chaperonin 60 protein family, and is predicted to be localized in chloroplasts.
The researchers found that ZmCpn60-3 is highly expressed in maize stems and tassels and can be induced by exogenous plant hormones, mycotoxins, and pathogens. To understand its role in disease resistance, they overexpressed ZmCpn60-3 in Arabidopsis, a model plant often used in genetic studies. The results were promising: the overexpression improved resistance to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), a bacterial pathogen, by inducing a hypersensitive response and the expression of salicylic acid (SA) signaling-related genes.
“Our data demonstrate that ZmCpn60-3 orchestrates plant immune responses through a dual mechanism,” Su explained. “It triggers a reactive oxygen species (ROS) burst while simultaneously activating SA-mediated signaling cascades, thereby synergistically enhancing host disease resistance.”
The team also found that treating maize protoplasts with flg22, a bacterial protein fragment, significantly upregulated the transcriptional levels of the PR1 defense gene in ZmCpn60-3-transfected cells. Moreover, the enhanced resistance phenotype in ZmCpn60-3-overexpressing transgenic lines was specifically abolished by pretreatment with ABT, an SA biosynthetic inhibitor, highlighting the crucial role of SA in this process.
Looking ahead, this research could have significant commercial impacts, particularly in the agricultural sector. By understanding and manipulating proteins like ZmCpn60-3, scientists may develop crops with enhanced disease resistance, leading to increased yields and reduced losses due to pathogens. This could be particularly beneficial in the energy sector, where crops like maize are used for biofuel production.
Additionally, preliminary data from yeast two-hybrid assays suggested that ZmCpn60-3 might bind to ZmbHLH118 and ZmBURP7, indicating its potential involvement in plant abiotic stress responses. This opens up new avenues for research into how plants cope with environmental stresses, which could further inform breeding programs aimed at developing more resilient crops.
As Su and his team continue to unravel the complexities of maize’s defense mechanisms, their work provides a valuable reference for understanding the resistance mechanisms of ZmCpn60-3 in plant responses to both abiotic and biotic stress. This research not only advances our scientific knowledge but also paves the way for practical applications that could benefit agriculture and the energy sector alike.